MATLAB SIMULINK 7 - DEVELOPING S-FUNCTIONS User's Guide download pdf (Page 48)

3 Writing S-Functions As C-MEX files

3-4

Writing Basic C MEX S-Functions

This secti on d iscusses bas ic C MEX S-f unctions, where basic means an

S-function that contains only the required S-function routines. However, the

contents of the routines can be as complex as you like. You have the freedomto

place any logic in S-function routines a s long as the routines conform to their

required formats. This section prese nts a basic C MEX S- function by showing

how to implement an S-function that takes i ts input and multiplies it by two

(see

matlabroot/simulink/src/timestwo.c).

Inthefollowingmodel,the

timestwo S-functionisusedtodouble theamplitude

of a sine wave and plot it in a sco pe:

Within the block dialog fo r the S-function,

timestwo has been s pecified as the

name; the parameters field i s empty.

The

timestwo S-function contains the S-function routines shown in this figure:

Start of simulation

mdlInitializeSizes

mdlInitializeSampleTimes

mdlOutputs

mdlTerminate

Simulatio n

loop

Initialization

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MATLAB SIMULINK 7 - DEVELOPING S-FUNCTIONS User's Guide Page 48